1. Field of the Invention
This invention relates to apparatus for transferring fluids and more particularly, this invention relates to apparatus for transferring ink utilizing air pressure.
2. Description of the Prior Art
During the processing of semiconductor devices, it is desirable to locate the individual devices on a semiconductor wafer which are defective. The individual devices, which are found to be defective, are marked with an ink dot and disposed of after the wafer is sliced to separate the individual devices. By disposing of the defective individual devices at this stage considerable cost savings and efficiencies are obtained because the defective devices are not packaged and then found defective. The devices are determined to be defective by an automatic tester called the prober. The tester, after determining that a particular individual device is defective, issues a signal to the inker which applies an ink dot to that individual device.
The prior inkers include a device having a stiff plastic line which is attached at one end to the moveable arm of a solenoid. From its attachment to the solenoid the line extends through a reservoir of ink and a hollow metal tube. When the solenoid is actuated, the end of the line adjacent to the end of the cylinder extends to contact the wafer at an individual defective device. When the solenoid is actuated, the line extending through the hollow metal tube utilizes wetting action and gravity to transfer ink from the interior of the hollow metal tube and thus the ink is transferred to the individual device. The ink with the hollow metal tube is resupplied by gravity from the reservoir. Although this type of inker functions, it does not provide uniform ink dots on the individual semiconductor devices. Further, the ink is exposed to the ambient air and drying can thereby occur. As the cost of processing semiconductor devices increases and with the introduction of more automated packaging equipment, it was desirable that a more dependable inker be developed which provided higher reliability and a more uniform ink dot size. It was also desirable that an inker be provided which had increased reliability eliminating intermittent failures.
None of the prior constructions known utilizes a pneumatic system for application of ink to mark individual semiconductor devices on a wafer. Further, none of the prior constructions shows utilizing a variable pulse of gas under pressure to a pneumatic system for expelling a predetermined amount of fluid.